The present invention relates generally to film processing, and more particularly to an improved system and method for producing printed copies of motion picture films by dye transfer.
In the field of professional cinematography, it is necessary under many circumstances that two lengths of film be kept in close and accurate register with one another throughout a lengthy continuous path. For example, in manufacturing a dye transfer print of a motion picture from three dye imbibed photographic matrices, it is essential that the dye image from each individual matrix be transferred to a receiver film in near perfect register with each other in three consecutive steps on a continuous machine. Further, it is also essential that each individual record is transferred completely from matrix to receiver film with substantially no movement of one film relative to the other, until such time as all of the image has been transferred from each individual matrix to the common receiver.
Previously, matrix and receiver films were placed in intimate contact with each other via a multi-stage seating mechanism generally known as a roll tank. While being placed into intimate contact with each other, the two films were also seated onto a stainless steel ribbon, known as a pin belt. The pin belt typically traveled in an orbital path extending around and between two or more drums or wheels. The perforations or sprocket holes of the sandwiched films were placed over silver alloy pins raised above the flat stainless steel ribbon. Both films remained firmly seated on the pin belt for the duration of time needed for complete dye transfer from matrix to receiver, generally about thirty five seconds.
Because of the time required for complete dye transfer, such pin belts generally had a peripheral length of about 205 feet and were operated at speeds of about 330 feet per minute. One of the difficulties resulting from using such long belts is achieving and maintaining the exacting pin tolerances necessary to hold the precise registration needed to produce high quality prints. In addition, repair and replacement of these long belts was indeed expensive and difficult. The machinery and methods used for dye transfer of color film prints has remained substantially unchanged since its original development in the 1920""s and 1930""s.
To obtain the faster throughput necessary to meet the demand for the larger quantities of prints required today, the operating speed of a dye transfer machine must be increased. A larger apparatus requiring a longer pin belt, however, would only magnify the problems of maintaining the exacting pin tolerances necessary to maintain precise registration during dye transfer. The space required for such an apparatus and the cost to manufacture and maintain the pin belt generally render such a system commercially impracticable.
For these and other reasons, the dye transfer process generally has become less favored than photographic copying processes. Conventional photographic copying of a master onto unexposed photographic films, such as nitrate, acetate, and more recently polyester films, are now widely used for producing the large number of prints needed for modern theater distribution, which can require more than 4,000 prints per film.
Photographic film processing, however, does not provide the precise color control of tone scale and color reproduction available using dye transfer processing, which may result in inferior color rendition in photographic film prints. Further, photographic film has a greater tendency to fade over time, resulting in a less durable print.
Accordingly, there is a need for an improved system for producing dye transfer prints of motion pictures that is capable of maintaining precise registration at high volume production speeds.
There is also, then, a need for a method of producing dye transfer prints of films competitively in sufficient quantities for the continuously growing need of motion picture theater distribution.
The present invention is directed to a system for producing printed copies of films by dye transfer. More particularly, the present invention is directed to an apparatus and method for maintaining sandwiched films, comprising a matrix film superimposed onto a receiver film, in precise registration during dye transfer, the predominance of which is accomplished without a pin belt.
Generally, a dye transfer apparatus in accordance with the present invention includes a roll tank having a first plurality of rollers in a predetermined orientation. The first plurality of rollers is adapted to superimpose a blank or receiver film onto a dye-imbibed matrix film in a predetermined registration, i.e. to place the receiver and matrix films in intimate contact, thereby creating a two-film xe2x80x9csandwichxe2x80x9d for dye transfer.
The roll tank communicates with a pin belt, which includes a plurality of pins or teeth on a ribbon traveling in an orbital path. The pins engage sprocket holes in the two-film sandwich delivered within the roll tank, thereby directing the two-film sandwich along a portion of the orbital path. The pins also have a predetermined spacing therebetween for maintaining the two-film sandwich in precise registration as they travel along the orbital path. A first stripping roller is provided in communication with the pin belt, which strips the two-film sandwich from the pin belt, while maintaining the films in precise registration and without adversely affecting the adhesion between the films.
A transfer cabinet then receives the two-film sandwich from the first stripping roller to substantially complete dye transfer. The transfer cabinet includes a second plurality of rollers having a predetermined relationship to one another, and an elevator mechanism for adjusting the predetermined relationship. The rollers in the transfer cabinet have relatively large diameters compared to the other rollers in the apparatus, thereby defining substantially rectilinear paths along their perimeters. The rollers define a film path along which the two-film sandwich travels through the transfer cabinet, the two-film sandwich traveling systematically around a portion of the perimeters of the rollers and between the rollers in a predetermined sequence. The rollers also preferably have substantially uniform, toothless perimeters, thereby allowing the two-film sandwich to travel along the perimeters thereof without requiring sprockets or teeth to engage the two-film sandwich, while maintaining the films in precise registration and without adversely affecting the adhesion between the films.
The elevator mechanism includes one or more servo-motors for precisely adjusting the position of one or more corresponding rollers within the transfer cabinet, thereby providing a predetermined tension on the two-film sandwich traveling along the film path. The elevator mechanism may be adjusted manually, or may include one or more sensors for measuring the actual tension of the two-film sandwich as it travels along the film path. Preferably, the transfer cabinet also includes a pair of synchronized servo-motors for adjusting the distribution of tension of the two film sandwich, thereby providing additional tension adjustment, and thereby further maintaining the two-film sandwich in precise registration and without adversely affecting the adhesion between the films.
The transfer cabinet also provides predetermined atmospheric conditions, such as a predetermined temperature and humidity, to promote complete dye transfer from the dye imbibed matrix to the receiver film as the two-film sandwich travels through the cabinet in a predetermined time.
A second stripping roller, including a third plurality of rollers in a predetermined orientation, is provided in communication with the film path of the transfer cabinet. The third plurality of rollers separate the matrix film from the receiver film after complete dye transfer has occurred substantially within the transfer cabinet.
The separated receiver film may then be processed using other apparatus and methods to provide a finished print. For example, the receiver film may be directed through a subsequent system similar to that just described to transfer an additional color to the receiver film. The matrix film may be directed through dying equipment, or a spray dye tank, and followed by a washback system enclosure, in preparation for dye transfer to a subsequent receiver film.
A dye transfer printing system in accordance with the present invention substantially reduces the length of pin belt necessary for an individual dye transfer path, and allows the system to operate at substantially higher speeds than traditional pin belt systems to produce film prints in substantially greater volume in a commercially feasible manner. For example, in one aspect, a roll tank in accordance with the present invention may include rollers having a predetermined hardness and which apply a predetermined pressure to the two-film sandwich to promote adhesion and/or dye transfer at substantially higher speeds than previous systems.
In addition, a pin belt in accordance with the present invention may have an orbital path or peripheral length substantially less than about 200 feet, and preferably about 22 feet. The pin belt includes specially designed and/or arranged pins adapted to facilitate seating and stripping of the films from the pin belt at relatively high speeds without substantial risk of damaging the films. Thus, the pin belt may be operated at speeds of about 800 feet per minute or more, and preferably between about 1,000 and 1,200 feet per minute, without substantial risk of damaging and/or misaligning the two-film sandwich during seating and subsequent stripping. These parameters result in the two-film sandwich being on the pin belt for not more than about 1 or 2 seconds, that is, substantially less than 10% of the about 45-50 seconds generally needed for complete dye transfer.
Thus, a dye transfer apparatus in accordance with the present invention substantially completes dye transfer without a pin registration device such as the pin belt, and preferably while the two-film sandwich is directed along a pinless substantially rectilinear path, such as within the transfer cabinet. The film path preferably has a length that is sufficiently long such that the two-film sandwich travel through the transfer cabinet in about 45-50 seconds, thereby allowing complete dye transfer to occur therein. The substantially rectilinear path defined by the relatively large diameter rollers and the natural adhesion of the films promoted by the tension adjustment provided by the elevator mechanism allow the transfer cabinet to maintain the two-film sandwich in precise registration without the need for pins or sprockets, thereby allowing the films to travel along the film path at substantially higher speeds than previously available.
Accordingly, a principal object of the present invention is to provide a dye transfer apparatus that substantially reduces the length of pin belt needed to maintain a matrix film and a receiver film in precise registration during dye transfer.
It is also an object to provide an improved apparatus and method for maintaining in precise registration a receiver film superimposed onto a dye imbibed matrix film as they travel at relatively high speeds along a continuous path;
It is also an object to provide an improved system for processing dye transfer prints of professional motion picture films at substantially higher speeds than those available using prior dye transfer systems.
It is also an object to provide an improved roll tank for seating a dye imbibed matrix film and a receiver film together to facilitate dye transfer under high speed conditions.
It is also an object to provide an improved pin belt for seating receiver and matrix films thereon, and for stripping the films therefrom under high speed conditions.
Other objects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings.